Yazdi M H, Johansson K, Gates P, Näsholm A, Jorjani H, Liljedahl L E
Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala.
J Anim Sci. 1999 Mar;77(3):533-40. doi: 10.2527/1999.773533x.
Variance and covariance components for birth weight (BWT), as a lamb trait, and litter size measured on ewes in the first, second, and third parities (LS1 through LS3) were estimated using a Bayesian application of the Gibbs sampler. Data came from Baluchi sheep born between 1966 and 1989 at the Abbasabad sheep breeding station, located northeast of Mashhad, Iran. There were 10,406 records of BWT recorded for all ewe lambs and for ram lambs that later became sires or maternal grandsires. All lambs that later became dams had records of LS1 through LS3. Separate bivariate analyses were done for each combination of BWT and one of the three variables LS1 through LS3. The Gibbs sampler with data augmentation was used to draw samples from the marginal posterior distribution for sire, maternal grandsire, and residual variances and the covariance between the sire and maternal grandsire for BWT, variances for the sire and residual variances for the litter size traits, and the covariances between sire effects for different trait combinations, sire and maternal grandsire effects for different combinations of BWT and LS1 through LS3, and the residual covariations between traits. Although most of the densities of estimates were slightly skewed, they seemed to fit the normal distribution well, because the mean, mode, and median were similar. Direct and maternal heritabilities for BWT were relatively high with marginal posterior modes of .14 and .13, respectively. The average of the three direct-maternal genetic correlation estimates for BWT was low, .10, but had a high standard deviation. Heritability increased from LS1 to LS3 and was relatively high, .29 to .37. Direct genetic correlations between BWT and LS1 and between BWT and LS3 were negative, -.32 and -.43, respectively. Otherwise, the same correlation between BWT and LS2 was positive and low, .06. Genetic correlations between maternal effects for BWT and direct effects for LS1 through LS3 were all highly negative and consistent for all parities, circa -.75. Environmental correlations between BWT and LS1 through LS3 were relatively low and ranged from .18 to .29 and had high standard errors.
作为羔羊性状的出生体重（BWT）以及初产、经产和三产母羊的产羔数（LS1至LS3）的方差和协方差分量，采用吉布斯抽样器的贝叶斯方法进行估计。数据来自1966年至1989年出生在伊朗马什哈德东北部阿巴斯阿巴德种羊场的俾路支羊。所有母羊羔和后来成为种公羊或外祖父的公羊羔都有10406条BWT记录。所有后来成为母羊的羊羔都有LS1至LS3的记录。对BWT与LS1至LS3这三个变量之一的每种组合进行了单独的双变量分析。采用带数据扩充的吉布斯抽样器，从父本、外祖父和残差方差以及BWT的父本与外祖父之间的协方差、产羔数性状的父本方差和残差方差以及不同性状组合的父本效应之间的协方差、BWT与LS1至LS3不同组合的父本和外祖父效应以及性状之间的残差协方差的边际后验分布中抽取样本。尽管大多数估计密度略有偏斜，但它们似乎与正态分布拟合良好，因为均值、众数和中位数相似。BWT的直接遗传力和母本遗传力相对较高，边际后验众数分别为0.14和0.13。BWT的三个直接-母本遗传相关估计值的平均值较低，为0.10，但标准差较高。遗传力从LS1到LS3增加，且相对较高，为0.29至0.37。BWT与LS1以及BWT与LS3之间的直接遗传相关为负，分别为-0.32和-0.43。否则，BWT与LS2之间的相同相关为正且较低，为0.06。BWT的母本效应与LS1至LS3的直接效应之间的遗传相关在所有胎次中均为高度负相关且一致，约为-0.75。BWT与LS1至LS3之间的环境相关相对较低，范围为0.18至0.29，且标准误差较高。
